The invention relates to a drag-type spreading apparatus for placing road construction mixtures, in particular bituminous cold mixtures, into depressions in a road surface, for example, in grooves in the lanes of a road surface. The drag-type spreading apparatus will hereafter be called spreader. The spreader has two skids rigidly connected a distance apart and extending in parallel to the working direction which is the advance direction of the spreader as the latter is pushed or pulled along the road by a suitable vehicle such as a tractor or bulldozer. The spreader also has a position adjustable screeding structure with a suitable configuration which opens in the working direction. The screeding structure includes a portion which inclines away from the working direction and the slope of the inclination is adjustable.
Such a spreader is described in the German Patent Publication No. 2,534,386. The known spreader has a screed, the ends of which face in the working direction and are pivotally mounted to the skids by means of coaxially arranged bolts. The known screed is adjustable relative to a cross beam connecting the skids.
The advantage of such a configuration is seen in that only a height adjusting means is required for an angular positioning of the screeding structure relative to the road surface. Hence, a quick adaptation to changing road construction requirements is possible.
Spreaders of this type are mainly used for placing or installing of bituminous cold materials, such as slurries or the like, particularly in track grooves in the lanes. Consequently, a more or less strongly distinct sorting of the mineral components of the material mixture occurs directly beneath the leveling plank. The mineral components are sorted from the edges toward the middle, ranging from fine to coarse, whereby the sorting is dependent on the depth of the groove.
Such a sorting is not only desired, rather, in view of the expected stability of the installed filler, it is required. The maintaining of a homogeneous condition of the mixture material in the spreader, however, is a prerequisite for such prior art approach. However, such homogeneous condition is very often not given, and a material which has already been separated cannot be sorted by such an apparatus.
The cold mixture material is very often a rather flowable material. In view of this, a negative effect of the pressure caused by the material in front of and in contact with the screeding structure may not always be positively avoided, especially in instances where grooves or holes of substantial depth must be filled. Thus, heretofore, the grooves in the lane are often overfilled and the excess material impairs the eveness of the repaired road surface.